Hydraulic machines such as excavators, dozers, loaders, backhoes, motor graders, and other types of heavy equipment use one or more hydraulic actuators to accomplish a variety of tasks. These actuators are fluidly connected to an engine-driven pump of the machine that provides pressurized fluid to chambers within the actuators. As the pressurized fluid moves into or through the chambers, the pressure of the fluid acts on hydraulic surfaces of the chambers to affect movement of the actuators and a connected work tool.
One problem associated with this type of hydraulic arrangement involves efficiency. In particular, there may be times when the hydraulic machine is idle and yet still operational. For example, during a truck loading cycle, when an excavator finishes loading a first truck, the excavator must wait for the first truck to depart and a second truck to arrive before additional loading tasks can be completed. And during this time, the engine of the machine may still be turned on (often at high speeds) and needlessly consuming fuel. In these situations, it may be beneficial to selectively turn the engine off to conserve fuel. However, after turning the engine off, it may take some time for the engine to be turned back on and ramp up to required speeds. And this time delay could result in lost productivity and/or become a nuisance for the operator.
An exemplary system for starting and stopping an engine is disclosed in W.O. Patent Application Publication No. 2012/125798 of Lowman et al. that published on Sep. 20, 2012 (“the '798 publication”). Specifically, the '798 publication discloses an engine driven hydraulic system having a first accumulator and a second accumulator connected to a pump that provides pressurized fluid to hydraulic implements. When it is determined that the hydraulic implements have not been activated by operator command for a given amount of time and the accumulators have satisfactory charging levels, fuel to the engine is shut off. As soon as it is determined that hydraulic flow to the implements needs to be resumed due to operator command, fluid stored in the first accumulator is directed through the pump to start the engine. Simultaneously, fluid from the second accumulator is directed to the implements to provide instantaneous operation.
Although the system of the '798 publication may improve machine operation by providing instantaneous use of the implements during engine startup, the system may still be less than optimal. In particular, because the accumulators are dedicated to a single purpose, the system may be bulky and expensive. In addition, because the accumulators are charged only with fluid from the pump, the system may have low efficiency.
The disclosed implement system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.